Thermally stable calcium-aluminum bulk amorphous metals with low mass density

ABSTRACT

The present invention relates to novel calcium based amorphous alloys with high thermal stability and low mass density represented by the general formula: CaAlQ, wherein Q represents one or more elements selected from the group consisting of Cu, Ag, Zn and Mg. Typically, the atomic percentage of the calcium is about 50%.

RELATED APPLICATIONS

This application claims priority under 35 USC § 119(e) to U.S.Provisional Application Ser. Nos. 60/477,605, filed Jun. 11, 2003,60/490,806, filed Jul. 29, 2003 and 60/524,506, filed Nov. 24, 2003, thedisclosures of which are incorporated herein by reference.

US GOVERNMENT RIGHTS

This invention was made with United States Government support under anAir Force Office of Scientific Research Contract No. F33615-01-2-5217awarded by the Defense Advance Research Projects Agency. The UnitedStates Government has certain rights in the invention.

BACKGROUND

Bulk-solidifying amorphous metal alloys (a.k.a. bulk metallic glasses)are those alloys that can form an amorphous phase upon cooling the meltat a rate of several hundred degrees Kelvin per second or lower.Amorphous alloys usually exhibit certain superior properties than theircrystalline counterparts with the same or similar compositions, such astensile or compressive strength, wear resistance and corrosionresistance as well as oxidation resistance. As promising structuralmaterials, the study of light-metal-based amorphous alloys has grown inthe past two decades. To date, light-metal-based amorphous alloys havebeen successfully prepared in several alloy systems, including Mg-TM-RE(wherein TM represents late transition metals, such as Cu and Ni, and RErepresents rare earth metals, such as Y and La), Al-TM-RE (including Ni,Co and Fe as the TM element and Gd and Y as the RE element), Al—Cu—Mg—Niand recently reported Ca—Cu—Mg alloys.

Table 1 lists the glass transition temperature Tg, onset temperature ofcrystallization Tx, reduced glass transition temperature Trg (defined asglass transition temperature over the melting point of the alloy inKelvin), calculated mass density (grams per cubic centimeter) and glassformability of several representative light-metal-based amorphous alloycompositions. The calculated mass density was obtained by assuming novolume contraction or expansion when alloying the component elementstogether. The glass formability was characterized by the diameter inmillimeters of the cast cylinder-shaped rod with a fully amorphousstructure or by the thickness of the ribbon-shaped samples with a fullyamorphous phase for those alloys whose glass formability is not highenough to form bulk amorphous samples. TABLE 1 Summary of representativelight-metal-based amorphous alloy compositions, together with Tg, Tx,Trg, calculated mass density and glass formability. Calculated Tg TxMass Glass Composition (at. %) (° C.) (° C.) Trg Density FormabilityAl₈₇Ni₇Gd(Y)₆ N/A 210 3.18-3.58 200-300 μm Al₈₅Ni₇Gd(Y)₈ 250 280 0.453.24-3.76 100-150 μm Mg₆₀Cu₃₀Y₁₀ 160 210 0.60 3.40 6 mm(Al₇₅Cu₁₇Mg₈)₉₅Ni₅ N/A 167 3.55 100 μm Ca₆₇Mg₁₉Cu₁₄ 114 134 0.60 1.92 2mm Ca₅₇Mg₁₉Cu₂₄ 131 167 0.64 2.24 ≧4 mmAll the alloys listed in Table 1, except Al₈₅Ni₇Gd(Y)₈ alloys, whichunfortunately is not a bulk glass former, exhibit quite low thermalstability. Their Tg, if observable, is much less than 200° C., withtheir Tx being at most near 200° C. From the practical point of view,the low thermal stability of the light-metal-based bulk amorphous alloysmentioned above has limited their application as structural materials.It is an attractive idea to develop light-metal-based amorphous alloyswhich simultaneously exhibit a large glass formability and a highthermal stability useful for structural applications.

SUMMARY OF VARIOUS EMBODIMENTS OF THE INVENTION

The present invention is directed to a new class of bulk amorphousalloys based on calcium and aluminum that exhibit large glassformability and high thermal stability and thus are useful forstructural applications. With variation of the composition, the massdensity of the CaAl-based bulk amorphous alloys ranges from 1.74 to 2.50grams/cc, which is among the lowest values reported for amorphousmetals. The thermal stability of CaAl-based amorphous alloys, having Alcontent of about 25-30 atomic percent, is much higher than those of theCa-based Al-free amorphous alloys (Tg=180-240° C.), while exhibitingglass formability that allows for the preparation of cast amorphous rodshaving a diameter of at least 1 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. represents a photograph of an as-cast 9 mm diameter amorphousrod of Ca₅₅Al₁₀Mg₁₅Zn₁₅Cu₅ alloy.

FIG. 2. illustrates an x-ray diffraction pattern from exemplary samplepieces (each of total mass about 1 gram) obtained by crushing a 2 mmas-cast rods of a bulk amorphous Ca_(56.5)Al_(28.5)Mg₁₀Cu₅ alloy.

FIG. 3. illustrates differential scanning calorimeter (DSC) curvesrepresenting the crystallization and melting behavior of high Al contentCaAl-based representative alloys as marked in the figure.

FIG. 4. represents enlarged DSC curves of FIG. 3 showing the glasstransition phenomenon of the high Al content CaAl-based representativealloys.

FIG. 5. illustrates differential scanning calorimeter (DSC) curvesrepresenting the crystallization and melting behavior of low Al contentCaAl-based representative alloys with compositions marked in the figure.

DETAILED DESCRIPTION OF EMBODIMENTS

Definitions

In describing and claiming the invention, the following terminology willbe used in accordance with the definitions set forth below.

As used herein, the term “reduced glass temperature (Trg)” is defined asthe glass transition temperature (Tg) divided by the liquidustemperature (Tl) in K.

As used herein, the term “supercooled liquid region (ΔTx)” is defined ascrystallization temperature minus the glass transition temperature.

As used herein, the term “calcium-based alloy” refers to alloys whereincalcium constitutes a major component of the alloy. Typically, thecalcium-based amorphous alloys of the present invention have a Cacontent of approximately 50% or greater, however, the Ca content of thepresent alloys may comprise anywhere from 35% to 75% calcium.

As used herein, the term “amorphous alloy” is intended to include bothcompletely amorphous alloys (i.e. where there is no ordering ofmolecules/atomic packing), as well as partially crystalline alloyscontaining crystallites that range from nanometer to the micron scale insize.

EMBODIMENTS

Aluminum-based amorphous alloys have been successfully prepared inseveral alloy systems, however the previous described light metal-basedbulk glass alloys suffer the disadvantage of exhibiting low thermalstability. Applicants have discovered a new class of bulk amorphousalloys based on calcium and aluminum that simultaneously exhibit largeglass formability and high thermal stability and thus are useful forstructural applications. Experimentally it was found that binary Ca—Alalloys, close to the Ca-rich eutectic composition range, are able toform bulk cylinder-shaped amorphous rods with a diameter up to 1 mm.This is believed to be the first report of the formation of bulkamorphous alloys in a binary metal system. With the further introductionof Cu, Ag, Mg and/or Zn, the glass formability of the alloys is improvedand the diameter of the cast amorphous rods varies from 3 to 9 mm,depending on the Al content of the alloys.

In one embodiment of the present invention a calcium-based aluminumamorphous alloy comprising at least 50% calcium is prepared usingcommercial grade material to create an alloy that can be processed intocylinder samples having a diameter of 1.0 millimeter or greater. In oneembodiment the calcium-based aluminum amorphous alloys of the presentinvention exhibit a Tg of at least 170° C. In one embodimentcalcium-based amorphous alloys comprise at least 50% calcium and 20-35%aluminum and exhibit a Tg greater than 200° C. In another embodiment acalcium-based amorphous alloy is provided, comprising at least 50%calcium and 10-20% aluminum, that can be cast as an amorphous rod havinga continuous diameter of about 3 to about 9 mm and exhibiting a Tggreater than 110° C. In one embodiment the bulk-solidifying Ca-basedamorphous alloys of the present invention are completely amorphous.Since the synthesis-processing methods employed by the present inventiondo not involve any special materials handling procedures, they aredirectly adaptable to low-cost industrial processing technology.

In accordance with one embodiment of the present invention, acalcium-based amorphous alloy with enhanced glass formability and highthermal stability properties is provided wherein the alloy isrepresented by the formula:Ca_((100-t))Al_(x)Cu_(y)Ag_(n)Zn_(m)Mg_(p)Ni_(r)  Iwherein

x, y, n, m, p and r are atomic percentages, wherein

-   -   x is a number selected from about 5 to about 35;    -   y is a number selected from 0 to about 15;    -   n, m, p and r are independently a number selected from 0 to        about 20, wherein y+n+m+p+r is less than 30; and

t is the sum of x, y, n, m, p and r, with the proviso that t is a numberselected from about 25 to about 55. In accordance with one embodiment,an alloy of the general formula I is provided wherein x is a numberselected from about 25 to about 40, r is 0, and y+n+m+p is less than 20.In accordance with one embodiment, an alloy of the general formula I isprovided wherein x is a number selected from about 30 to about 40 and y,n, m, r and p are each 0.

In accordance with another embodiment, a calcium-based amorphous alloyis provided wherein the alloy is represented by the formula:Ca_((100-t))Al_(x)Q_(g)  II

wherein Q is an element selected from the group consisting of Cu, Ag, Znand Mg;

x is a number selected from about 25 to about 35;

g is a number selected from 0 to about 15; and

t is the sum of x and g.

In accordance with one embodiment, a calcium-based amorphous alloy isprovided wherein the alloy is represented by the formula:Ca_((100-t))Al_(x)Cu_(y)Ag_(n)Zn_(m)Mg_(p)  IIIwherein

x, y, n, m and p are atomic percentages, wherein

-   -   x is a number selected from about 25 to about 35;    -   p is a number selected from about 5 to about 15;    -   n, m and y are independently a number selected from 0 to about        20, wherein y+n+m+p is less than 30; and

t is the sum of x, y, n, m and p, with the proviso that t is a numberselected from about 25 to about 55.

In accordance with one embodiment, an alloy of the general formula IIIis provided wherein x is a number selected from about 25 to about 35, yand m are independently a number selected from 0 to about 10, n is anumber selected from 0 to about 15, p is a number selected from 0 toabout 20, and t is the sum of x, y, n, m and p, with the proviso that tis a number selected from about 25 to about 55.

In a further embodiment a calcium-based amorphous alloy that exhibit aTg greater than 200° C. is provided wherein the alloy has the generalstructure of formula III. More particularly in one embodiment an alloyof the general formula III is provided wherein x is a number selectedfrom about 27 to about 32, y and n are independently a number selectedfrom 0 to about 5, m is 0, p is about 10 to about 20, and t is a numberselected from about 43 to about 47. In another embodiment an alloy ofthe general formula III is provided wherein x is a number selected fromabout 27 to about 30, y and n are independently a number selected from 0to about 5, m is 0, p is about 10 to about 15, and t is a numberselected from about 43 to about 44. In another embodiment an alloy ofthe general formula III is provided wherein x is a number selected fromabout 27 to about 30, n is a number selected from 0 to about 10, y and mare both 0, p is about 10 to about 15, and t is a number selected fromabout 43 to about 44. In another embodiment an alloy of the generalformula III is provided wherein x is a number selected from about 27 toabout 32, n, y and m are each 0, p is about 10 to about 15, and t is anumber selected from about 42 to about 45.

In another embodiment a light-metal-based amorphous alloy is providedthat has superior glass formability, allowing for the formation ofamorphous rods with diameters ranging from greater than 2 mm to about 9mm. Such calcium-based amorphous alloys are represented by the generalformula:Ca_((100-t))Al_(x)Cu_(y)Ag_(n)Zn_(m)Mg_(p)Ni_(r)  Iwherein

x, y, n, m, p and r are atomic percentages, wherein

-   -   x is a number selected from about 5 to about 15;    -   p is a number selected from about 5 to about 15;    -   r is a number selected from 0 to about 10;    -   n, m and y are independently a number selected from 0 to about        20, wherein y+n+m is less than about 21; and

t is the sum of x, y, n, m, p and r, with the proviso that t is a numberselected from about 35 to about 55. In accordance with one embodiment acalcium/aluminum-based amorphous alloy is provided that has superiorglass formability, wherein the alloy is represented by formula I whereinx is a number selected from about 5 to about 15, y is a number selectedfrom 0 to about 15, n is 0, m is a number selected from about 10 toabout 20, p is a number selected from about 10 to about 15, r is anumber selected from 0 to about 10, and t is a number selected fromabout 35 to about 50.

In accordance with one embodiment, a calcium-based amorphous alloy isprovided wherein the alloy is represented by the formula:Ca_(t)Al_(x)Q_(y)Zn_(m)Mg_(p)  IVwherein Q is Cu or Ni;

t, x, y, m and p are atomic percentages, wherein

-   -   t is a number selected from about 50 to about 60;    -   x is a number selected from about 10 to about 15;    -   y is a number selected from about 5 to about 10;    -   m is a number selected from about 10 to about 20; and    -   p is a number selected from 10 to about 15.        In accordance with one embodiment a calcium/aluminum-based        amorphous alloy is provided that has superior glass formability,        wherein the alloy is represented by formula IV wherein t is a        number selected from about 55 to about 60, x is about 10, y is a        number selected from 0 to about 10, m is a number selected from        about 10 to about 20 and p is a number selected from about 10 to        about 15.

The CaAl-based bulk amorphous alloys of the present invention can beformulated to generate higher thermal stability or higher glassformability properties by manipulating the aluminum content of thealloy. More particularly, “high Al” content alloys, containing 25-35atomic percent Al, exhibit a thermal stability much higher than those ofthe Ca-based Al-free amorphous alloys. Typically, the high Al amorphousalloys exhibit a Tg of greater than 200° C. and a Tx ranging from about220 to about 270° C. “Low Al” content alloys, containing 5-15 atomicpercent Al, are able to form amorphous rods having a diameter of atleast 3 mm and up to about 9 mm. These low Al content Ca—Al amorphousalloys exhibit a Tg ranging from 120 to 150° C. and Tx from 150 to morethan 200° C., and thus they exhibit greater glass formability at thesacrifice of some of the thermal stability. However, these low Alamorphous alloys are better suited in GFA than previously describedCa-alloys.

With variation of the composition, the mass density of the CaAl-basedbulk amorphous alloys ranges from 1.74 to 2.50 grams/cc, which is amongthe lowest values reported for amorphous metals. Preliminary measurementof the CaAl-based amorphous alloys shows that the microhardness is inthe range of 200-240/DPH. According to the empirical relationshipbetween the microhardness value and the mechanical strength, theseamorphous alloys are expected to exhibit a fracture tensile strengtharound 700-800 MPa This value is about 40% higher than that of thepreviously disclosed Ca-based Al-free amorphous alloys, where acompressive fracture strength of 545 MPa was reported for the alloyCa₅₇Mg₁₉Cu₂₄. The good combination of large glass formability, low massdensity, high thermal stability and mechanical properties indicates thatthe CaAl-based amorphous alloys could be a promising structural materialwhere comprehensive properties are required.

The present alloys may be devitrified to form amorphous-crystallinemicrostructures, or infiltrated with other ductile phases duringsolidification or melting of the amorphous alloys in thesupercooled-liquid region, to form composite materials, which can resultin strong hard products with improved ductility for structuralapplications. In accordance with one embodiment of the invention, thealloys can be made to exhibit the formation of quasi-crystals uponcooling at a rate somewhat slower than the critical cooling rate forglass formation. In this case, the alloy can solidify into a compositestructure consisting of quasi-crystalline precipitates embedded in anamorphous matrix. In this way, high strength bulk quasi-crystallinematerials can be produced and thus the range of practical applicationsis extended. For example, quasi-crystalline materials typically havevery low coefficients of friction and high hardness, making them usefulfor bearing applications.

In accordance with one embodiment of the present invention, an articleof manufacture is provided wherein the article comprises alight-metal-based amorphous alloy represented by the formula:Ca_((100-t))Al_(x)Cu_(y)Ag_(n)Zn_(m)Mg_(p)Ni_(r)  Iwherein

x, y, n, m, p and r are atomic percentages, wherein

-   -   x is a number selected from about 5 to about 15;    -   p is a number selected from about 5 to about 15;    -   r is a number selected from 0 to about 10;    -   n, m and y are independently a number selected from 0 to about        20, wherein y+n+m is less than about 21; and

t is the sum of x, y, n, m, p and r, with the proviso that t is a numberselected from about 35 to about 55. In accordance with one embodiment acalcium/aluminum-based amorphous alloy is provided that has superiorglass formability, wherein the alloy is represented by formula I whereinx is a number selected from about 5 to about 15, y is a number selectedfrom 0 to about 15, n is 0, m is a number selected from about 10 toabout 20, p is a number selected from about 10 to about 15, r is anumber selected from 0 to about 10, and t is a number selected fromabout 35 to about 50.

In accordance with another embodiment, an article of manufacture isprovided wherein the article comprises a calcium-based amorphous alloyrepresented by the formula:Ca_(t)Al_(x)Q_(y)Zn_(m)Mg_(p)  IVwherein Q is Cu or Ni;

t, x, y, m and p are atomic percentages, wherein

-   -   t is a number selected from about 50 to about 60;    -   x is a number selected from about 10 to about 15;    -   y is a number selected from about 0 to about 10;    -   m is a number selected from about 10 to about 20; and    -   p is a number selected from 10 to about 15.

In accordance with another embodiment, an article of manufacture isprovided wherein the article comprises a CaAl-based amorphous alloyrepresented by the formula:Ca_((100-t))Al_(x)Cu_(y)Ag_(n)Zn_(m)Mg_(p)wherein

x, y, n, m and p are atomic percentages, wherein

-   -   x is a number selected from about 25 to about 35;    -   n is a number selected from about 0 to about 20;    -   m and y are independently a number selected from 0 to about 15,    -   p is a number selected from about 0 to about 20; and

t is the sum of x, y, n, m and p, with the proviso that t is a numberselected from about 30 to about 50.

Owing to the good glass formability, CaAl-based alloys can be producedinto various forms of amorphous alloys, such as thin ribbon samples bymelt spinning, amorphous powders by atomization, amorphous rods, sheetsand/or plates by casting. The casting can be carried out usingconventional injection casting, die casting, squeeze casting, suctioncasting and strip casting as well as other state-of the-art castingtechniques currently employed in research labs and industries. Owing tothe existence of a distinct supercooled liquid region, it is verypromising to utilize the formability of the CaAl-based amorphous alloysin the supercooled liquid region to form desired shapes of frames andparts without further machining.

The combination of low mass density, high thermal stability andmechanical properties as well as good glass formability make the presentCaAl-based amorphous alloys promising structural materials havingapplications where high comprehensive properties are required. Thealloys can be used in a variety of applications including use ascoatings to provide oxidation and/or corrosion resistant layers and useas structural materials under extreme environments. Ceramic particles orfibers and/or refractory metal particles can be blended with atomizedCaAl-based alloy powders, and by extrusion, used to produce compositematerials for structural applications. Alternatively, the present alloysmay be devitrified partially to form amorphous-crystalline compositematerials.

The present CaAl-based amorphous alloys may be used in many applicationareas. Some of the products and services to which the present inventioncan be implemented include, but are not limited thereto 1) vehicle(land-craft and aircraft) frames and parts, 2) engineering,construction, and medical materials and tools and devices, 3) laminatecomposite: laminate with other structural alloys (e.g. Mg, Al, Fe, andTi to name a few) for aerospace applications, 4) other utilizations thatrequire the combination of specific properties realizable by the presentCa-based amorphous alloys. CaAl-based metallic glasses may also haveother useful functional applications in addition to their mechanicalproperties. As important as its potential practical application, fromthe scientific point of view, CaAl-based amorphous alloys (especiallythe binary Ca—Al alloy), provide an ideal system to study thefundamental issues related to glass formability of alloy systems.

EXAMPLE 1

Preparation of CaAl-Based Amorphous Alloys

Ingot Preparation

Alloy ingots were prepared by melting mixtures of high purity elementsin an induction furnace. Boron-nitride-coated graphite crucibles areused as the melting boat in the preparation of alloy ingots. For the Cuand Ag-containing alloys, Cu and Ag elements are placed on the top ofthe raw materials. Because Cu and Ag are materials with the highestmelting points in these alloy system, they will be the last ones to bemelted during melting. Arranging the elements in this way allows directobservation of the melting of Cu and/or Ag, which then react with themelted material, assuring a homogeneous composition.

Glass Formability

The amorphous samples were produced preliminarily via conventionalcopper mold casting, which is realized by injecting the alloy melt intoa cylinder-shaped cavity inside a water-cooled copper block. Thermaltransformation data were acquired using a Differential Scanningcalorimeter (DSC). The designed CaAl-based amorphous alloys exhibit areduced glass transition temperature Trg in the range 0.56-0.63 and asupercooled liquid region ΔT in the range 20-50° C. The alloys of thisinvention can be cast into amorphous rods with diameters reaching up to3-9 mm, depending on the Al content employed. A picture of the 9 mmas-cast amorphous rod of Ca₅₅Al₁₀Mg₁₅Zn₁₅Cu₅ alloy is shown in FIG. 1.The amorphous nature of the cast rods is verified by x-ray diffractionand DSC measurement (see FIGS. 2 through 5).

EXAMPLE 2

High Al Content (25-35 at. %) Ca—Al-Based Alloys

With Al as the main additive, the strong interaction of Al with Ca andthe unique network microstructure between Ca and Al atoms give the highthermal stability of the designed amorphous alloys. Introducingadditional elements such as Mg, Cu, Ag, Zn, further improves the glassformability of the alloys, resulting in binary (CaAl), ternary (CaAlCu,CaAlAg, CaAlMg, CaAlZn), quaternary (CaAlCuAg, CaAlMgCu, CaAlMgAg,CaAlMgZn and CaAlCu(Ag)Zn) and quinary (CaAlMgCuAg, CaAlMgCuZn andCaAlMgAgZn) alloys. Exemplary alloys include those represented by thefollowing formulas (in atomic percent)

Binary Alloys

Ca_(100-x)Al_(x)

where 32≦x≦37

Ternary Alloys

Ca_(100-x-y)Al_(x)Cu(Ag,Mg,Zn)_(y)

where 27≦x≦35, 0≦y≦20

Quaternary Alloys

Ca_(100-x-y)Al_(x)(A_(a)B_(b))_(y)

where 27≦x≦35, 0≦y≦17, 0≦a,b≦100, and AB represents combinations ofCuAg, MgCu, MgAg, MgZn, CuZn or AgZn.

Quinary Alloys

Ca_(100-x-y-z)Al_(x)Mg_(y)(A_(a)B_(b))_(z)

where 27≦x≦35, 5≦y≦15, 5≦z≦15, 0≦a,b≦100, AB represents combinations ofCuZn or AgZn.

These alloys are found to exhibit a Tg=180-240° C., Tx=200-270° C., andTrg=0.56-0.61 (applicable only for those alloys that show a glasstransition). Typical XRD pattern of the cast amorphous rods is shown inFIG. 2. Curves of differential scanning calorimeter (DSC) analysisshowing the glass transition, crystallization and melting behavior aregiven in FIGS. 3 and 4. It is interesting to note that binary Ca—Alamorphous alloys possess the highest thermal stability. However, furtherintroduction of Cu, Ag, Mg and/or Zn increase the glass formability ofthis alloy system. The diameter of the cast rods with a fully amorphousstructure increases from 1 mm for binary alloys to 3 mm for multinaryalloys. The addition of Ag helps to extend the supercooled liquidregion, with ΔT=48° C. for Ca₆₀Al₃₀Ag₁₀. A number of typical amorphousalloys are listed in Table 2, together with their Tg (if observable), Txand the glass formability characterized by the diameter (in mm) of thecast rod with a fully amorphous structure.

EXAMPLE 3

Low Al Content Ca—Al-Based Alloys

The low Al content CaAl alloys are composed of at least four components.With decreasing the Al content to the range of 5 to 15 atomic percent,and at the same time, mainly increasing Zn content to replace Al, thedesigned alloys are given in the following formula:Ca_(x)Al₅₋₁₅Mg_(y)Zn_(z)Cu_(s)(Ni)_(t)

where 50<x<65, 10<y<15, 10<z<20, 0≦s<15 and 0≦t<10.

The thermal stability of the obtained amorphous alloys was decreasedwhen compared to the high Al content alloys, with Tg ranging from 120 to150° C. and Tx from 150 to 200° C. or above. However, the glassformability was greatly improved, resulting in alloys that can be castinto 9 mm diameter amorphous rods. FIG. 1 shows a picture of the as-cast9 mm amorphous rod of Ca₅₅Al₁₀Mg₁₅Zu₁₅Cu₅ alloy. FIG. 5 presents aseries of DSC curves of the low Al content CaAl alloys where the glasstransition, crystallization and melting behavior are shown. A number oftypical amorphous alloys are listed in Table 3, together with their Tg(if observable), Tx and the glass formability characterized by thediameter (in mm) of the cast rod with a fully amorphous structure.

Both high and low Al content Ca—Al alloys possess a low mass density.The calculated mass density of the alloys ranges from 1.74 to 2.50gram/cc. The calculation is done by neglecting the possible volumecontraction and expansion effect when alloying these component elementstogether.

Preliminary measurement indicated that the microhardness of theinvention amorphous alloys is in the range 200-240 DPH. The fracturestrength has not been evaluated yet. According to the empirical rulebetween the microhardness value and the mechanical property, thefracture tensile strength is expected to be on the level of 700-800 MPa.TABLE 2 Thermal data obtained from differential thermal analysis (DTA)scans of High Al content Ca-based bulk amorphous alloys. Calculated TgTx Diameter of mass density Composition (at. %) (° C.) (° C.) amorphousrod (gram/cc) Ca_(66.4)Al_(33.6) 255 267 1 mm 1.74 Ca₅₅Al₃₀Cu₁₅ N/A 2061 mm 2.17 Ca₆₀Al₃₀Cu₁₀ 225 244 1.5 mm 2.00 Ca₅₅Al₃₅Cu₁₀ N/A 244 1 mm2.05 Ca₆₅Al₃₀Cu₅ N/A 242 1 mm 1.85 Ca₆₃Al₃₂Cu₅ 230 257 2 mm 1.87Ca₆₀Al₃₀Ag₁₀ 210 258 2 mm 2.20 Ca₆₃Al₃₂Ag₅ 230 254 1.5 mm 1.96Ca₆₀Al₃₀Mg₁₀ 235 250 2 mm 1.74 Ca₆₀Al₃₀Zn₁₀ 225 257 1.5 mm 1.99Ca₅₅Mg₁₀Al₃₀Cu₅ N/A 216 1 mm 2.02 Ca₅₈Al₃₂Mg₁₀ 240 266 1.5 mm 1.75Ca₅₅Al₃₀Mg₁₅ 240 262 1 mm 1.75 Ca₅₈Al₂₇Mg₁₅ 230 255 1.5 mm 1.73Ca_(56.5)Al_(28.5)Mg₁₅ 230 255 1.5 mm 1.74 Ca₅₆Al₂₉Mg₅Cu₁₀ N/A 206 1 mm2.01 Ca₅₃Al₂₇Mg₁₀Cu₁₀ N/A 197 1 mm 2.02 Ca_(56.5)Al_(28.5)Mg₁₀Cu₅ 220247 3 mm 1.87 Ca_(56.5)Al_(28.5)Ag₁₅ 210 238 1 mm 2.45 Ca₆₀Al₃₀Cu₅Ag₅215 242 1 mm 2.10 Ca_(56.5)Al_(28.5)Ag₁₀Cu₅ 170 194 1 mm 2.35Ca_(62.5)Al_(31.5)Cu₄Ag₂ 220 250 1.5 mm 1.93 Ca₆₀Al₃₀Ag₈Cu₂ 205 248 1.5mm 2.16 Ca₅₃Al₂₇Mg₁₀Ag₁₀ 205 230 1.5 mm 2.22 Ca_(56.5)Al_(28.5)Mg₁₀Ag₅215 242 3 mm 1.97 Ca_(54.5)Al_(27.5)Mg₁₀Ag₈ 205 238 2 mm 2.12Ca_(55.5)Al_(29.5)Mg₁₀Ag₅ 216 248 2 mm 1.98 Ca_(57.5)Al_(27.5)Mg₁₀Ag₅220 255 2 mm 1.96 Ca_(54.5)Al_(30.5)Mg₁₀Ag₅ 220 257 1.5 mm 1.99Ca_(53.5)Al_(31.5)Mg₁₀Ag₅ 220 257 1.5 mm 2.00 Ca₅₃Al₂₇Mg₁₅Ag₅ 210 2281.5 mm 1.98 Ca₅₃Al₂₇Mg₁₅Cu₅ 220 240 1.5 mm 1.88 Ca₅₃Al₂₇Mg₁₃Ag₇ 200 2241 mm 2.07 Ca₅₃Al₂₇Mg₁₇Ag₃ 220 245 1 mm 1.88 Ca_(56.5)Al_(28.5)Mg₁₀Zn₅230 250 1.5 mm 1.87 Ca_(56.5)Al_(28.5)Mg₅Zn₅Cu₅ 215 235 1 mm 2.00Ca_(56.5)Al_(28.5)Mg₅Zn₅Ag₅ 210 240 1.5 mm 2.10

TABLE 3 Thermal data obtained from differential thermal analysis (DTA)scans of Low Al content Ca-based bulk amorphous alloys. Calculated Tg TxDiameter of mass density Composition (at. %) (° C.) (° C.) amorphous rod(gram/cc) Ca₆₀Al₅Mg₁₅Zn₂₀ 127 159 7 mm 2.11 Ca₅₅Al₁₀Mg₁₅Zn₂₀ 137 189 5mm 2.17 Ca₅₅Al₁₀Mg₁₅Zn₁₅Cu₅ 127 159 9 mm 2.17 Ca₅₅Al₁₀Mg₁₅Zn₁₀Cu₁₀ 120138 7 mm 2.18 Ca₅₅Al₁₀Mg₁₅Zn₁₇Cu₃ 135 163 7 mm 2.17Ca₅₅Al₁₀Mg₁₅Zn_(12.5)Cu_(7.5) 116 137 7 mm 2.17 Ca₅₅Al₁₀Mg₁₅Zn₁₅Ni₅ 131169 7 mm 2.16 Ca₅₀Al₁₅Mg₁₅Zn₁₅Cu₅ 136 189 3 mm 2.22 Ca₅₅Al₁₅Mg₁₀Zn₁₅Cu₅141 200 3 mm 2.19 Ca₅₅Al₁₅Mg₁₅Zn₁₀Cu₅ 130 148 3 mm 2.06

1. An amorphous alloy represented by the formula:Ca_((100-t))Al_(x)Cu_(y)Ag_(n)Zn_(m)Mg_(p)Ni_(r) wherein x, y, n, m, pand r are atomic percentages, wherein x is a number selected from about5 to about 35; y is a number selected from 0 to about 15; n, m, p and rare independently a number selected from 0 to about 20, whereiny+n+m+p+r is less than 30; and t is the sum of x, y, n, m, p and r, withthe proviso that t is a number selected from about 25 to about
 55. 2.The alloy of claim 1, wherein r is
 0. 3. The alloy of claim 1, whereinsaid alloy is processable into bulk amorphous samples of at least about2 mm in thickness in its minimum dimension.
 4. The alloy of claim 1,wherein said alloy has a Tg of at least 200° C.
 5. The alloy of claim 2,wherein x is a number selected from about 25 to about 40, and y+n+m+p isless than
 20. 6. The alloy of claim 5 wherein the alloy is representedby the formula:Ca_((100-t))Al_(x)Q_(g) wherein Q is an element selected from the groupconsisting of Cu, Ag, Zn and Mg; x is a number selected from about 25 toabout 35; g is a number selected from 0 to about 15; and t is the sum ofx and g.
 7. The alloy of claim 6 wherein g is
 0. 8. The alloy of claim 1wherein the alloy is represented by the formula:Ca_(t)Al_(x)Q_(y)Zn_(m)Mg_(p) wherein Q is Cu or Ni; t, x, y, m and pare atomic percentages, wherein t is a number selected from about 50 toabout 60; x is a number selected from about 5 to about 15; y is a numberselected from about 0 to about 10; m is a number selected from about 10to about 20; and p is a number selected from 10 to about
 15. 9. Thealloy of claim 8 wherein t is a number selected from about 55 to about60, and p is about
 15. 10. An article of manufacture comprising acalcium-based amorphous alloy represented by the formula:Ca_((100-t))Al_(x)Cu_(y)Ag_(n)Zn_(m)Mg_(p)Ni_(r) wherein x, y, n, m, pand r are atomic percentages, wherein x is a number selected from about5 to about 35; p is a number selected from about 5 to about 15; r is anumber selected from 0 to about 10; y, n and m are independently anumber selected from 0 to about 20, wherein y+n+m is less than about 21;and t is the sum of x, y, n, m, p and r, with the proviso that t is anumber selected from about 35 to about
 55. 11. The article ofmanufacture of claim 10 wherein x is a number selected from about 5 toabout 15; y is a number selected from 0 to about 15; n is 0; m is anumber selected from about 10 to about 20; p is a number selected fromabout 10 to about 15; r is a number selected from 0 to about 10, and tis a number selected from about 35 to about
 50. 12. The article ofmanufacture of claim 11 wherein the calcium-based amorphous alloy isrepresented by the formula:Ca_(t)Al_(x)Q_(y)Zn_(m)Mg_(p) wherein Q is Cu or Ni; t, x, y, m and pare atomic percentages, wherein t is a number selected from about 50 toabout 60; x is a number selected from about 10 to about 15; y is anumber selected from about 0 to about 10; m is a number selected fromabout 10 to about 20; and p is a number selected from 10 to about 15.13. The article of manufacture of claim 10 wherein the calcium-basedamorphous alloy is represented by the formula:Ca_((100-t))Al_(x)Cu_(y)Ag_(n)Zn_(m)Mg_(p) wherein x, y, n, m and p areatomic percentages, wherein x is a number selected from about 25 toabout 35; n is a number selected from about 0 to about 20; m and y areindependently a number selected from 0 to about 15, p is a numberselected from about 0 to about 20; and t is the sum of x, y, n, m and p,with the proviso that t is a number selected from about 35 to about 50.14. A method of preparing homogeneous ingots of a CaAl-based amorphousalloy comprising Cu or Ag, said method comprising the steps of placingall the elements of the alloy, except the Cu and Ag elements in aboron-nitride-coated graphite crucible; placing the Cu and Ag elementsin the crucible on top of, and in contact with, the other alloyelements; and melting the combination together to form a homogenousingot.